Asus’s 1,920 x 1,080, 15.6inch panel is a tremen­dous lap­top add-on for one key rea­son: you can power it and send sig­nal to it via a sin­gle USB-C con­nec­tor. The case con­verts to a stand, too, for true por­ta­ble con­ve­nience. £200, asus.com

AOC E1759FWU

This AOC is huge at 17 inches, cheap, and com­pat­i­ble with just about ev­ery lap­top since it works fine with older USB con­nec­tors; but don’t ex­pect stel­lar per­for­mance un­less you’re on a mod­ern ma­chine. Driv­ing its 1,600 x 900 res at USB 2.0 speeds causes some dis­play lag. £132, aoc-europe.com